Method and apparatus for listening based transmission

ABSTRACT

Embodiments of the present disclosure relate to a method for listening-based transmission. The method is performed at a communications device of a first type with a plurality of beams and operable on an unlicensed spectrum. The method comprises identifying a beam direction for a communications device of a second type when there is data directed to the communications device of the second type and obtaining a backoff counter for the identified beam direction. The method also comprises selecting at least one beam direction for listening during. The beam in each of the at least one beam direction covers at least one communications device of the second type having data directed thereto. The method further comprises scheduling transmission to a communications device of the second type in the identified beam direction when the backoff counter corresponding to that beam direction reaches a certain threshold. Embodiments also relate to corresponding apparatus.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 15/028,871,filed Apr. 12, 2016, which is a National stage of InternationalApplication No. PCT/CN2015/086224, filed Aug. 6, 2015, which are herebyincorporated by reference.

TECHNICAL FIELD

The non-limiting and exemplary embodiments of the present disclosuregenerally relate to the technical field of wireless communications, andspecifically to a method and apparatus for transmission based on beamspecific listening in a wireless network utilizing beamforming and anunlicensed spectrum.

BACKGROUND

This section introduces aspects that may facilitate better understandingof the disclosure. Accordingly, the statements of this section are to beread in this light and are not to be understood as admissions about whatis in the prior art or what is not in the prior art.

Mobile broadband will continue to drive the demand for a higher overalltraffic capacity and a higher achievable end-user data rate in radioaccess networks. Several scenarios in the future will require data ratesof up to 10 Gbps in local areas. Thus, an objective to be realized bynext generation networks, which may be referred to as the fifthgeneration (5G) systems, is to meet such demand for the high trafficcapacity and the high end-user date rate.

As one key technique, high-gain beamforming, typically implemented witharray antennas, may be used in the next generation networks to mitigatethe increased path loss at higher frequencies. Moreover, the nextgeneration networks are also expected to be operating on the unlicensed(shared) spectrum in addition to the traditional licensed (exclusive)spectrum. It has been agreed to study Licensed-Assisted Access (LAA)technologies in the 3GPP at RP-141664. This LAA framework builds oncarrier aggregation solutions introduced in LTE Release-10 to access theadditional bandwidth in the unlicensed spectrum. Accordingly, a supportfor coexistence of the licensed and unlicensed spectrums is needed toenable spectrum sharing between different operators or systems.Currently, the Listen-Before-Talk (LBT) mechanism is the most flexibleway to achieve this coexistence support, since it is a distributedmechanism such that there is no need for exchanging information betweendifferent operators or systems, which is costly and complicated.

The LBT mechanism is commonly used in Wi-Fi systems. Wi-Fi works with nophysical wired connection between a sender and a receiver by using radiofrequency (RF) technology. In Wi-Fi systems, an access point usually hasa range of about 20 meters indoors and a greater range outdoors. Wi-Fisystems are defined as wireless local area network (WLAN) products basedon Institute of Electrical and Electronics Engineers (IEEE) 802.11standards.

According to IEEE 802.11 standards, the basic media access control (MAC)protocol employs a Carrier Sense Multiple Access with CollisionAvoidance (CSMA/CA)-based LBT mechanism. FIG. 1 illustrates the LBTmechanism used in the current Wi-Fi systems. As illustrated, the sameprotocol is applied by all stations in both downlink (DL) and uplink(UL). A station, e.g. a user equipment (UE) that wishes to transmit apacket first senses the medium. If the medium is sensed idle for acertain time (the so-called Distributed Inter Frame Space (DIFS), e.g.50 μs for 802.11b), the packet is then transmitted. If the medium isbusy, the station defers until the medium is sensed idle. When thisoccurs, the station does not transmit immediately, since it may lead tocollisions if more than one station was deferring. Instead, the stationsets a backoff timer to a random value, and does not transmit until thistimer has expired. The backoff timer is only decreased when the mediumis sensed idle. Whenever the medium is sensed busy, a deferment state isentered where the backoff timer is not decreased. When the backoff timerexpires, the packet will be transmitted. If the packet is successfullyreceived by a receiving station, it responds with an acknowledgement tothe transmitting station. The acknowledgement is sent a Short InterFrame Space (SIFS), e.g. 10 μs for 802.11b, after the packet isreceived. Since SIFS<DIFS, no other station will access the mediumduring this time. If no acknowledgement is received by the transmittingstation, because either the packet itself or the acknowledgement waslost, the transmitting station generates a new backoff, and retransmitsthe packet when the backoff timer has expired. Even if the packet wassuccessfully acknowledged, the transmitter will generate a backoff andwait for it to expire before transmitting the next packet. The backofftime is measured in units of slot times, which for 802.11b are 20 μslong.

The current Wi-Fi systems are operating at low frequencies and thus boththe “listen” and “talk” can be omni-directional. Therefore, the keyobjective of the LBT in Wi-Fi systems is to avoid interference betweensimultaneous data transmission. Practical application results show thatthe current LBT mechanism works well in Wi-Fi systems.

However, if the CSMA/CA based LBT is applied in the next generationnetworks at higher frequencies, due to directional transmission withbeamforming, there will be some problems which do not exist in Wi-Fisystems. Therefore, a more efficient and effective LBT mechanism isneeded for data transmission in the next generation networks withmultiple beams and operable on the unlicensed spectrum, e.g. the LAAnetworks.

SUMMARY

Various embodiments of the disclosure aim at providing an efficient andeffective LBT mechanism for use in a wireless network that utilizesbeamforming and the unlicensed spectrum. Other features and advantagesof embodiments of the disclosure will also be understood from thefollowing description of specific embodiments when read in conjunctionwith the accompanying drawings, which illustrate the principles ofembodiments of the present disclosure.

In a first aspect of the present disclosure, there is provided a methodfor listening-based transmission. The method is performed at acommunications device of a first type with a plurality of beams andoperable on an unlicensed spectrum. Particularly, the method comprisesidentifying a beam direction for a communications device of a secondtype when there is data directed to the communications device of thesecond type and obtaining a backoff counter for the identified beamdirection. The method further comprises selecting at least one beamdirection for listening. During the listening, the backoff countercorresponding to the selected at least one beam direction may bechanged. The beam in each of the selected at least one beam directioncovers at least one communications device of the second type that hasdata directed thereto. Then, the method comprises schedulingtransmission to a communications device of the second type in theidentified beam direction when the backoff counter corresponding to thatbeam direction reaches a certain threshold.

By virtue of the method according to the first aspect of the presentdisclosure, the networks or systems with a plurality of beams, i.e.utilizing beamforming and operable on the unlicensed spectrum mayperform beam-specific listening instead of node-specific listening andthereby can make the best use of transmission opportunities in differentbeam directions without modifying too much of the traditional LBTprotocol.

In an embodiment, the backoff counter may be obtained for the identifiedbeam direction by generating the backoff counter for the identified beamdirection, if no backoff counter exists for that beam direction andotherwise, retrieving the existing backoff counter for the identifiedbeam direction.

In a further embodiment, the method may further comprise dividingcommunications devices of the second type connected to thecommunications device of the first type into at least one group eachcorresponding to a beam direction, before identifying the beam directionfor the communications device of the second type. In this embodiment,the beam direction may be identified for the communications device ofthe second type by determining the group to which the communicationsdevice of the second type belongs.

In another embodiment, the at least one beam direction for listening maybe selected based further on priorities of beam directions each coveringat least one communications device of the second type.

In yet another embodiment, the priority of a beam direction may bedetermined based on any one or any combination of: a quality of servicerequirement of a group of communications devices of the second typecorresponding to that beam direction; historical scheduling informationfor the group of communications devices of the second type correspondingto that beam direction; a channel quality of the beam in that beamdirection; a value of the backoff counter corresponding to that beamdirection; and a time when the communications device of the second typein that beam direction requests data.

According to the above embodiment, the beam directions may be selectedfor listening in consideration of multiple factors in various aspects.

In yet another embodiment, the method may further comprise judgingwhether a number of pending beam directions each covering at least onecommunications device of the second type that has data directed thereto,is greater than a number of receiving radio frequency chains of thecommunications device of the first type, before selecting the at leastone beam direction for listening. In this embodiment, if the number ofpending beam directions is greater than the number of receiving radiofrequency chains, then a number of the selected at least one beamdirection is equal to the number of receiving radio frequency chains;otherwise the number of the selected at least one beam direction isequal to the number of pending beam directions.

According to this embodiment, the beam directions can be selected forlistening within the limit of receiving radio frequency chains availableat the transmitter side, i.e. the communications device of the firsttype, so as to take full advantage of the available radio resources.

In yet another embodiment, the method may further comprise obtaining adeferring time period for a beam direction of the selected at least onebeam direction by performing virtual carrier sensing, if the number ofpending beam directions is greater than the number of the receivingradio frequency chains. During the deferring time period, the listeningfor that beam direction is suspended. Then, it may be switched to listento another beam direction among at least one unselected beam directioneach covering at least one communications device of the second type thathas data directed thereto during at least the deferring time period. Theother beam direction has a highest priority among the at least oneunselected beam direction.

In this way, when the transmission in a beam direction needs to bedeferred, e.g. due to interference from transmission of anothercommunications device, the transmission in another beam direction may beconducted without waiting for the other communications device tocomplete its transmission. This is referred to as “beam-specific”deferment, which can increase the spatial reuse efficiency brought bydirectional transmission using high gain beamforming, thereby ensuringfairness and efficient use of channel resources.

In yet another embodiment, the method may further comprise updating thebackoff counter for the beam direction that has ever been listened to.In this way, repetitive or even endless waiting in some certain beamdirections, for example those frequently subject to interference, may beavoided.

In a second aspect of the present disclosure, there is provided anapparatus for listening-based transmission. The apparatus is implementedat a communications device of a first type with a plurality of beams andoperable on an unlicensed spectrum. Particularly, the apparatuscomprises an identifying unit, an obtaining unit, a selecting unit, anda scheduling unit. The identifying unit is configured to identify a beamdirection for a communications device of a second type when there isdata directed to the communications device of the second type. Theobtaining unit is configured to obtain a backoff counter for theidentified beam direction. The selecting unit is configured to select atleast one beam direction for listening. During the listening, thebackoff counter corresponding to the at least one beam direction may bechanged. The beam in each of the at least one beam direction covers atleast one communications device of the second type having data directedthereto. The scheduling unit is configured to schedule transmission to acommunications device of the second type in the identified beamdirection when the backoff counter corresponding to that beam directionreaches a certain threshold.

In a third aspect of the present disclosure, there is provided anapparatus for listening-based transmission. The apparatus is implementedat a communications device of a first type with a plurality of beams andoperable on an unlicensed spectrum. The apparatus comprises a processorand a memory. The memory contains instructions executable by theprocessor, whereby the apparatus is operative to perform the method ofthe first aspect of the present disclosure.

In a fourth aspect of the present disclosure, there is provided anapparatus for listening-based transmission. The apparatus is implementedat a communications device of a first type with a plurality of beams andoperable on an unlicensed spectrum. The apparatus comprises processingmeans adapted to perform the method of any of the first aspect of thepresent disclosure.

In a fifth aspect of the present disclosure, there is provided acomputer program product comprising instructions which, when executed onat least one processor, cause the at least one processor to carry outthe method of the first aspect of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and benefits of variousembodiments of the disclosure will become more fully apparent from thefollowing detailed description with reference to the accompanyingdrawings, in which like reference numerals or letters are used todesignate like or equivalent elements. The drawings are illustrated forfacilitating better understanding of the embodiments of the disclosureand not necessarily drawn to scale, in which:

FIG. 1 illustrates the LBT mechanism used in Wi-Fi systems;

FIG. 2 shows a scenario for illustrating a possible problem when theexisting LBT mechanism applied for directional transmission;

FIG. 3 illustrates timing for transmission of AN 1 and AN 2 in FIG. 2;

FIG. 4 illustrates a flowchart of a method for listening-basedtransmission according to embodiments of the present disclosure;

FIG. 5 shows a specific example of switching beam directions forlistening according to an embodiment of the present disclosure;

FIG. 6 illustrates a schematic block diagram of an apparatus forlistening-based transmission according to embodiments of the presentdisclosure; and

FIG. 7 illustrates a simplified block diagram of another apparatusaccording to embodiments of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, the principle and spirit of the present disclosure will bedescribed with reference to the illustrative embodiments. It should beunderstood, all these embodiments are given merely for the skilled inthe art to better understand and further practice the presentdisclosure, but not for limiting the scope of the present disclosure.For example, features illustrated or described as part of one embodimentmay be used with another embodiment to yield still a further embodiment.In the interest of clarity, not all features of an actual implementationare described in this specification.

References in the specification to “an embodiment,” “anotherembodiment,” “yet another embodiment,” etc., indicate that theembodiment described may include a particular feature, structure, orcharacteristic, but every embodiment may not necessarily include theparticular feature, structure, or characteristic. Moreover, when aparticular feature, structure, or characteristic is described inconnection with an embodiment, it is submitted that it is within theknowledge of one skilled in the art to affect such feature, structure,or characteristic in connection with other embodiments whether or notexplicitly described.

It shall be understood that, although the terms “first” and “second”etc. may be used herein to describe various elements, these elementsshould not be limited by these terms. These terms are only used todistinguish one element from another. For example, a first element couldbe termed a second element, and similarly, a second element could betermed a first element, without departing from the scope of exampleembodiments. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed terms.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to limit example embodiments. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”,“comprising”, “has”, “having”, “includes” and/or “including”, when usedherein, specify the presence of stated features, elements, and/orcomponents etc., but do not preclude the presence or addition of one ormore other features, elements, components and/or combinations thereof.

In the following description and claims, unless defined otherwise, alltechnical and scientific terms used herein have the same meaning ascommonly understood by one of ordinary skill in the art to which thisdisclosure belongs. For example, the term “base station” used herein mayrefer to e.g. Access Node (AN), eNB, eNodeB, NodeB, Base TransceiverStation (BTS) or Access Point and the like, depending on the technologyand terminology used. Likewise, the term “terminal device” or UE usedherein may refer to any terminal having wireless communicationscapabilities, including but not limited to, mobile phones, cellularphones, smart phones, or personal digital assistants (PDAs), portablecomputers, image capture devices such as digital cameras, gamingdevices, music storage and playback appliances and any portable units orterminals that have wireless communications capabilities, or Internetappliances permitting wireless Internet access and browsing and thelike. Hereafter, the terms “terminal device” and “UE” may be usedinterchangeably and the terms “base station” and “AN” may be usedinterchangeably.

FIG. 2 shows a scenario for illustrating a possible problem when theexisting LBT mechanism applied for directional transmission implementedby beamforming. As shown, AN 1 attempts to transmit towards its servedUE 1 and UE 2 using directional transmission. It is assumed that AN 1can only transmit in one direction at one time and there is an ongoingtransmission initiated from AN 2 which will be interfering with thetransmission from AN 1 to UE 1. Following the existing LBT protocol, AN1 should perform random backoff to sense a channel state before startingthe transmission. Since the transmission of AN 2 is interfering with AN1, the channel state sensed by AN 1 will be busy. In this case, AN 1will have to defer its access to the channel until the data transmissionof AN 2 is finished.

FIG. 3 illustrates the timing for transmission of AN 1 and AN 2 in FIG.2. As shown, the access deferment is applied to AN 1, which meanstransmissions to both UE 1 and UE 2 will be deferred. In this case, eventhough the transmission from AN 1 to UE 2 is not interfered by thetransmission of AN 2, it still has to wait for AN 2 to complete itstransmission since the deferment is specific to the whole node. That is,the transmission opportunity from AN 1 to UE 2 is a waste due to this“node-specific” deferment. This type of “node-specific” deferment maydecrease the spatial reuse efficiency brought by directionaltransmission using high gain beamforming.

Furthermore, another problem with the existing LBT mechanism when it isapplied to networks with multiple beams using beamforming is how tolisten in different beam directions with limited receiving radiofrequency (RF) chains at the transmitter side, which is important forthe overall system performance.

In order to solve at least part of the above problems, a newtransmission solution based on a beam-specific LBT mechanism accordingto embodiments of the present disclosure will be described withreference to FIGS. 4-7.

FIG. 4 illustrates a flowchart of a method 400 for listening-basedtransmission according to embodiments of the present disclosure. Themethod 400 may be implemented either at a base station for transmissiondirected to a terminal device in DL or at the terminal device fortransmission directed to the base station in UL. Both the base stationand the terminal device support beamforming and operating on anunlicensed spectrum. In the following description, the base station orthe terminal device on which the method 400 is implemented will bereferred to as a communications device of a first type with a pluralityof beams and operable on an unlicensed spectrum. The other party towhich the transmission is directed will be referred to as acommunications device of a second type.

In FIG. 4, operations in blocks with a solid line are essential whileoperations in blocks with a broken line are optional depending onvarious embodiments of the present disclosure. The description will bestarted from the essential operation in block 410.

As illustrated, the method 400 enters at block 410, in which a beamdirection is identified at the communications device of the first type,e.g. the base station, for a communications device of the second type,e.g. a UE connected to the base station, when there is data directed tothe communications device of the second type.

As an example, in which the communications device of the first type is abase station and the communications device of the second type is a UE,there may be a beacon broadcast by the base station in the beam sweepingway with a reference signal in each beam. Then, the UE connected to thebase station will measure receiving power of the reference signal andreport identification (ID) of the corresponding beam in which thereference signal is received with the best receiving power. Based on thereported beam ID, the base station may identify a beam direction for theUE.

In an embodiment, before identifying the beam direction for thecommunications device of the second type having data directed thereto,all communications devices of the second type connected to thecommunications device of the first type may be divided, at block 405,into at least one group each corresponding to a beam direction.Accordingly, by determining which group the communications device of thesecond type that has data directed thereto belongs to, the beamdirection corresponding to the determined group may be identified as thebeam direction for that communications device of the second type.

As an example, in which the communications device of the first type is abase station and the communications device of the second type is a UE,multiple UEs connected to the base station may be divided into at leastone group according to their measurement reports. For example, there maybe a beacon broadcast by the base station in the beam sweeping way witha reference signal in each beam. Then, each of the UEs connected to thebase station will measure receiving power of the reference signal andreport identification (ID) of the corresponding beam in which thereference signal is received with the best receiving power. Based on thereported beam IDs, the base station may combine the UEs with the samereported beam ID into a same group.

As another example, multiple connected UEs may be divided into multiplegroups, for example according to their positions. The UEs in the same orsimilar direction may be formed into one group.

Subsequently, at bock 420, a backoff counter is obtained for theidentified beam direction.

In an embodiment, a backoff counter may be generated for the identifiedbeam direction, if no backoff counter exists for that beam direction.Preferably, in order to avoid collision, the backoff counter may begenerated randomly.

In another embodiment that there is an existing backoff counter for theidentified beam direction, the backoff counter may be obtained byretrieving the existing backoff counter for that beam direction.

For example, a table may be maintained at the communications device ofthe first type for recording the backoff counter. Once the beamdirection is identified for a communications device of the second type,the table may be checked to find whether there is already a backoffcounter for that beam direction and to retrieve the correspondingbackoff counter if there exists. One example of such a table is shown inTable 1.

TABLE 1 Beam Direction Generated backoff Updated backoff ID UE groupcounter counter 1 UE1, UE2 25 20 2 UE3 X X 3 UE4, UE5 18 10

Table 1 lists correspondences between beam directions and UE groups aswell as statuses of associated backoff counters. In Table 1, UE1 and UE2belong to a first UE group corresponding to beam direction 1; UE3belongs to a second UE group corresponding to beam direction 2; and UE4and UE 5 belong to a third UE group corresponding to beam direction 3. Anumber in the column “generated backoff counter” represents an initialvalue of the backoff counter generated for the corresponding beamdirection, wherein “X” represents that no backoff counter exists for thecorresponding beam direction. A number in the column “updated backoffcounter” represents a value of the corresponding backoff counter when itwas last updated, wherein “X” represents that no backoff counter existsfor the corresponding beam direction.

In this example, there is data for transmission to UE1, UE4 and UE5.Since UE1 belongs to the first UE group corresponding to beam direction1 while UE4 and UE5 belong to the third UE group corresponding to beamdirection 3, the base station may easily identify beam direction 1 forUE1 and beam direction 3 for UE4 and UE5 by checking Table 1 anddetermining the groups to which UE 1, UE 4 and UE 5 belong. Afterfurther checking Table 1, the base station may find out that therealready exist backoff counters for beam directions 1 and 3, and thenretrieve the backoff counter with a value 20 for the identified beamdirection 1 and retrieve the backoff counter with a value 10 for theidentified beam direction 3. As for UE3, if there is data directed toit, the base station may identify beam direction 2 for UE3 and find outthat no backoff counter exists for beam direction 2. In this case, thebase station may generate a backoff counter with a random value for beamdirection 2.

Once the backoff counter is obtained for the identified beam direction,at least one beam direction will be selected at block 430 for listening.During the listening, the backoff counter corresponding to the at leastone beam direction may be changed, e.g. decreased. The beam in each ofthe selected at least one beam direction covers at least onecommunications device of the second type that has data directed thereto.Note that, “the beam in a beam direction” may be regarded as a beamdirection with a certain width and thus the expression “the beam in abeam direction covers a communications device of the second type” andsimilar expressions will be simplified as the expression “a beamdirection covers a communications device with the second type” and thelike in this document.

In an embodiment, the at least one beam direction may be selected forlistening based on priorities of beam directions each covering at leastone communications device of the second type that has data directedthereto. The higher the priority of a beam direction is, the morepossible that beam direction is selected.

The priority of a beam direction may be determined based on any one orany combination of the following:

-   -   A QoS requirement of a group of communications devices of the        second type corresponding to the beam direction. In an example        that the communications device of the second type is a UE, if a        UE group corresponding to the beam direction has a delay        sensitive service, this group will have a higher priority.        Looking back to Table 1, if data directed to UE4 is delay        sensitive, then beam direction 3 will have a higher priority        than beam direction 1.    -   Historical scheduling information for the group of        communications devices of the second type corresponding to the        beam direction. For example, if data transmission for a UE group        is scheduled more often for a previous time, the beam direction        corresponding to this UE group has a lower priority. Looking        back to Table 1, if data transmission for UE1 is scheduled for        more times than UE4 and UE5, then beam direction 1 has a lower        priority than beam direction 3.    -   A channel quality of the beam in the beam direction. Generally,        a higher channel quality means that the beam direction has a        higher priority.    -   A value of the backoff counter corresponding to the beam        direction. Generally, a smaller value of the backoff counter        means that the corresponding beam direction has a higher        priority.    -   A time when the communications device of the second type in the        beam direction requests data. Generally, the communications        device which requests data at the earlier time will have a        higher priority.

In another embodiment, before the at least one beam direction isselected for listening, it may be judged at block 425 whether a numberof pending beam directions each covering at least one communicationsdevice of the second type that has data directed thereto, is greaterthan a number of receiving RF chains of the communications device of thefirst type. If the number of the pending beam directions is greater thanthe number of the receiving RF chains, then a number of the selected atleast one beam direction is equal to the number of the receiving RFchains; otherwise the number of the selected at least one beam directionis equal to the number of the pending beam directions.

In an example as shown with Table 1, assuming that the communications ofthe first type is a base station having more than two RF chains forreception, then the base station may select both beam direction 1 andbeam direction 3 simultaneously for listening. If the base station hasonly one RF chain for reception, the base station may select only one ofbeam directions 1 and 3 with the highest priority for listening.

In a further embodiment, if the number of the pending beam directions isgreater than the number of the RF chains, the communications device ofthe second type may obtain a deferring time period for a beam directionof the selected at least one beam direction by performing virtualcarrier sensing. The virtual carrier sensing is a well-known techniquefor collision avoidance, which is defined in 802.11 standards and willnot be detailed herein for the sake of brevity. During this deferringtime period, the listening for the beam direction is suspended. Then thecommunications device of the second type may switch at block 435 tolisten to another beam direction among at least one unselected beamdirection each covering at least one communications device of the secondtype that has data directed thereto during at least the deferring timeperiod. The other beam direction has a highest priority among the atleast one unselected beam direction.

Subsequently at block 440, transmission to a communications device ofthe second type in the identified beam direction is scheduled when thebackoff counter corresponding to that beam direction reaches a certainthreshold, for example, when the backoff counter is decreased to 0.

FIG. 5 shows a specific example of switching beam directions forlistening according to an embodiment of the present disclosure.

In this example, it is assumed that AN 1 has only one receiving RFchain; both UE 1 and UE 2 have data directed thereto; and beam direction1 corresponding to UE 1 has a higher priority than beam direction 2corresponding to UE 2. According to method 400, AN 1 first selects beamdirection 1 for listening. Upon decoding the Request to Send (RTS) fromAN 2, AN 1 is aware that there will be transmission of AN 2 that willinterfere with the transmission from AN 1 to UE 1. Thus, the directionaltransmission from AN 1 to UE 1 will have to be deferred by AN 1.Accordingly, a deferring time period may be obtained for beam direction1. During this deferring time period, the listening for beam direction 1is suspended and meanwhile beam direction 2 corresponding to UE2 will beselected for listening. If the backoff counter for beam direction 1 hasalready started before the deferment, this backoff counter may be heldduring the deferring time period. In this case, if the table forrecording the backoff counter like Table 1 is used, the backoff counterwill be updated at the time when the backoff counter is held and itsupdated value will be recorded in the table.

After the transmission from AN 1 to UE 2 in beam direction 2 completes,AN 1 may switch back to beam direction 1 for continuing the listening,since beam direction 1 has a higher priority.

Alternatively, if AN 1 is not transmitting when the deferring timeperiod ends, AN 1 may prioritize the beam directions again and selectthe beam direction with the highest priority for listening.

In this way, different from the scenario as shown in FIG. 2, thetransmission to UE 2 does not need to be deferred and contrarily, may beconducted without waiting for AN 2 to complete its transmission. This isreferred to as “beam-specific” deferment, which can increase the spatialreuse efficiency brought by directional transmission using high gainbeamforming, thereby ensuring the maximum channel capacity, fairness andQoS.

Additionally and preferably, the backoff counter for the beam directionthat has ever been listened to may be updated at block 445. As listed inTable 1, the updated backoff counter is recorded so that thecommunications device of the first type may obtain the latest value ofthe backoff counter, which may avoid repetitive or even endless waitingin some beam directions, for example those beam directions that arefrequently interfered by transmissions from an adjacent communicationsdevice.

By virtue of method 400 according to various embodiments of the presentdisclosure, the networks or systems with a plurality of beams, i.e.utilizing high gain beamforming and operable on the unlicensed spectrummay make the best use of the transmission opportunities in differentbeam directions without modifying too much of the traditional LBTprotocol.

For the purpose of illustration only, FIG. 4 shows the method 400 in acertain order. However, those skilled in the art shall appreciate thatthe order for performing the method 400 is not limited thereby. Instead,some operations may be performed in parallel or in a reverse order. Forexample, the operation in block 425 may be performed in parallel with orbefore the operation in block 410 or 420; and the operations in blocks440 and 445 may be performed in parallel or in a reverse order.

FIG. 6 illustrates a schematic block diagram of an apparatus 600 forlistening-based transmission according to embodiments of the presentdisclosure. The apparatus 600 may be implemented at a base station fortransmission directed to a terminal device in DL or at the terminaldevice for transmission directed to the base station in UL. Both thebase station and the terminal device support beamforming and operatingon an unlicensed spectrum. In the following description, the basestation or the terminal device at which the apparatus 600 is implementedwill be referred to as a communications device of a first type with aplurality of beams and operable on an unlicensed spectrum. The otherparty to which the transmission is directed will be referred to as acommunications device of a second type.

In FIG. 6, various units in blocks with a solid line are essential whileunits in blocks with a broken line are optional depending on variousembodiments of the present disclosure.

Particularly, the apparatus 600 comprises an identifying unit 610, anobtaining unit 620, a selecting unit 630, and a scheduling unit 640.

The identifying unit 610 is configured to identify a beam direction fora communications device of a second type when there is data directed tothe communications device of the second type. The obtaining unit 620 isconfigured to obtain a backoff counter for the identified beamdirection. The selecting unit 630 is configured to select at least onebeam direction for listening. During the listening, the backoff countercorresponding to the at least one beam direction may be changed. Thebeam in each of the at least one beam direction covers at least onecommunications device of the second type having data directed thereto.The scheduling unit 640 is configured to schedule transmission to acommunications device of the second type in the identified beamdirection when the backoff counter corresponding to that beam directionreaches a certain threshold.

In an embodiment, the obtaining unit 620 may be configured to generate abackoff counter for the identified beam direction, if no backoff counterexists for that beam direction and otherwise, to retrieve the existingbackoff counter for the identified beam direction.

In a further embodiment, the apparatus 600 may further comprise adividing unit 605 that may be configured to divide communicationsdevices of the second type connected to the communications device of thefirst type into at least one group each corresponding to a beamdirection. In this embodiment, the identifying unit 610 may further beconfigured to identify the beam direction for the communications deviceof the second type by determining the group to which that communicationsdevice of the second type belongs.

In another embodiment, the selecting unit 630 may be configured toselect the at least one beam direction for listening based further onpriorities of beam directions each covering at least one communicationsdevice of the second type that has data directed thereto.

In a further embodiment, the priority of a beam direction may bedetermined based on any one or any combination of: a quality of servicerequirement of a group of communications devices of the second typecorresponding to that beam direction; historical scheduling informationfor the group of communications devices of the second type correspondingto that beam direction; a channel quality of the beam in that beamdirection; a value of the backoff counter corresponding to that beamdirection; and a time when the communications device of the second typein that beam direction requests data.

In yet another embodiment, the apparatus may further comprise a judgingunit 625 configured to judge whether a number of pending beam directionseach covering at least one communications device of the second type thathas data directed thereto, is greater than a number of receiving radiofrequency chains of the communications device of the first type. In thisembodiment, if the number of said pending beam directions is greaterthan the number of the receiving radio frequency chains, then a numberof the selected at least one beam direction is equal to the number ofthe receiving radio frequency chains; otherwise the number of theselected at least one beam direction is equal to the number of said beamdirections.

In yet another embodiment, the apparatus 600 may further comprise aswitching unit 635 that is configured to obtain a deferring time periodfor a beam direction of the selected at least one beam direction byperforming virtual carrier sensing, if the number of said pending beamdirections is greater than the number of the receiving radio frequencychains. During the deferring time period, the listening for the beamdirection is suspended. The switching unit 635 may further be configuredto switch to listen to another beam direction among at least oneunselected beam direction each covering at least one communicationsdevice of the second type that has data directed thereto during at leastthe deferring time period. The other beam direction has a highestpriority among the at least one unselected beam direction.

In yet another embodiment, the apparatus 600 may further comprise anupdating unit 645 that is configured to update the backoff counter forthe beam direction that has ever been listened to.

The above units 605-645 may be configured to implement the correspondingoperations or steps as described above in relation to the method 400 andthus will not be detailed herein for the sake of brevity.

FIG. 7 illustrates a simplified block diagram of an apparatus 700. Theapparatus 700 may be embodied at or as at least part of a base stationfor transmission directed to a terminal device in DL. The apparatus 700may alternatively embodied at or as at least a part of a terminal devicefor transmission directed to a base station in UL. Both the base stationand the terminal device support a plurality of beams and are operable onan unlicensed spectrum.

Particularly, the apparatus 700 comprises at least one processor 710,such as a data processor (DP) and at least one memory (MEM) 720 coupledto the processor 710. The apparatus 700 may further comprise atransmitter TX and receiver RX 730 coupled to the processor 710 forestablishing communications with other apparatuses. The MEM 720 stores aprogram (PROG) 740. The PROG 740 may include instructions that, whenexecuted on the associated processor 710, enable the apparatus 700 tooperate in accordance with the embodiments of the present disclosure,for example to perform the method 400, depending on the specificimplementation of the apparatus 700. A combination of the at least oneprocessor 710 and the at least one MEM 720 may form processing means 750that is adapted to implement the embodiments of the present disclosure.

The MEM 720 may be of any type suitable to the local technicalenvironment and may be implemented using any suitable data storagetechnology, such as semiconductor based memory devices, magnetic memorydevices and systems, optical memory devices and systems, fixed memoryand removable memory, as non-limiting examples.

The processors 710 may be of any type suitable to the local technicalenvironment, and may include one or more of general purpose computers,special purpose computers, microprocessors, digital signal processors(DSPs) and processors based on multicore processor architecture, asnon-limiting examples.

Further, the present disclosure may also provide a computer programproduct comprising instructions that when executed by a processing unitin a base station or terminal device causes the base station or terminaldevice to perform the method 400.

In addition, the present disclosure may also provide a carriercontaining the computer program as mentioned above, wherein the carrieris one of an electronic signal, optical signal, radio signal, orcomputer readable storage medium. The computer readable storage mediumcan be, for example, an optical compact disk or an electronic memorydevice like a RAM (random access memory), a ROM (read only memory),Flash memory, magnetic tape, CD-ROM, DVD, Blue-ray disc and the like.

The techniques described herein may be implemented by various means sothat an apparatus implementing one or more functions of a correspondingapparatus described with an embodiment comprises not only prior artmeans, but also means for implementing the one or more functions of thecorresponding apparatus described with the embodiment and it maycomprise separate means for each separate function, or means that may beconfigured to perform two or more functions. For example, thesetechniques may be implemented in hardware (one or more apparatuses),firmware (one or more apparatuses), software (one or more modules), orcombinations thereof. For a firmware or software, implementation may bemade through modules (e.g., procedures, functions, and so on) thatperform the functions described herein.

Exemplary embodiments herein have been described above with reference toblock diagrams and flowchart illustrations of methods and apparatuses.It will be understood that each block of the block diagrams andflowchart illustrations, and combinations of blocks in the blockdiagrams and flowchart illustrations, respectively, can be implementedby various means including computer program instructions. These computerprogram instructions may be loaded onto a general purpose computer,special purpose computer, or other programmable data processingapparatus to produce a machine, such that the instructions which executeon the computer or other programmable data processing apparatus createmeans for implementing the functions specified in the flowchart block orblocks.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyimplementation or of what may be claimed, but rather as descriptions offeatures that may be specific to particular embodiments of particularimplementations. Certain features that are described in thisspecification in the context of separate embodiments can also beimplemented in combination in a single embodiment. Conversely, variousfeatures that are described in the context of a single embodiment canalso be implemented in multiple embodiments separately or in anysuitable sub-combination. Moreover, although features may be describedabove as acting in certain combinations and even initially claimed assuch, one or more features from a claimed combination can in some casesbe excised from the combination, and the claimed combination may bedirected to a sub-combination or variation of a sub-combination.

It will be obvious to a person skilled in the art that, as thetechnology advances, the inventive concept can be implemented in variousways. The above described embodiments are given for describing ratherthan limiting the disclosure, and it is to be understood thatmodifications and variations may be resorted to without departing fromthe spirit and scope of the disclosure as those skilled in the artreadily understand. Such modifications and variations are considered tobe within the scope of the disclosure and the appended claims. Theprotection scope of the disclosure is defined by the accompanyingclaims.

What is claimed is:
 1. A method to be implemented in a communicationdevice of a first type, comprising: obtaining back-off counter values,wherein each back-off counter value is mapped to a respective one of aplurality of beam directions and indicates a medium idle duration in arespective beam direction, wherein when a number of pending beamdirections of the communication device of the first type is greater thana number of receiving radio frequency chains of the communication deviceof the first type, the plurality of the beam directions is equal to thenumber of receiving radio frequency chains, and otherwise the pluralityof the beam directions is equal to the number of pending beamdirections; simultaneously listening to the plurality of beam directionswhile updating the respective back-off counter values, each beamdirection covering at least one respective communication device of asecond type, to which data is to be transmitted; and schedulingtransmission of data to a communications device of the second type in abeam direction within the plurality of beam directions, when therespective back-off counter value mapped to the beam direction reaches acertain threshold.
 2. The method of claim 1, further comprising:identifying the beam direction for the communication device of thesecond type by determining a beam identification (ID) from thecommunication device of the second type, which reports the beam IDmapped to the beam direction, which has the best receiving power asmeasured by the communication device of the second type.
 3. The methodof claim 2, wherein the communication device of the first type groups aplurality of communication devices of the second type each reporting thesame beam ID.
 4. The method of claim 2, further comprising: broadcastinga reference signal to the plurality of beam directions, each beamdirection corresponding to one of a plurality of beams of thecommunication device of the first type.
 5. The method of claim 1,wherein a respective back-off counter value for the beam directionwithin the back-off counter values is obtained by: receiving a valuethat is less than a generated back-off counter value, wherein thegenerated back-off counter value has been updated to the value from anearlier listening session.
 6. The method of claim 5, further comprising:in the earlier listening session, listening to the beam direction whiledecreasing the generated back-off counter value; upon interference beingdetected in the beam direction, suspending the listening for the beamdirection and stopping the decrease; storing the decreased value; andlistening to another beam direction for transmission to anothercommunication device of the second type.
 7. The method of claim 6,wherein the beam direction has a higher priority than the another beamdirection.
 8. An apparatus at a communications device of a first type,the apparatus comprising: a processor and a non-transitory computerreadable storage medium containing instructions, which when executed onthe processor, cause the apparatus to perform: obtaining back-offcounter values, wherein each back-off counter value is mapped to arespective one of a plurality of beam directions and indicates a mediumidle duration in a respective beam direction, when a number of pendingbeam directions of the communication device of the first type is greaterthan a number of receiving radio frequency chains of the communicationdevice of the first type, the plurality of the beam directions is equalto the number of receiving radio frequency chains, and otherwise theplurality of the beam directions is equal to the number of pending beamdirections; simultaneously listening to the plurality of beam directionswhile updating the back-off counter values, each beam directionscovering at least one respective communication device of a second type,to which data is to be transmitted; and scheduling transmission of datato a communications device of the second type in a beam direction withinthe plurality of beam directions, when the respective back-off countervalue mapped to the beam direction reaches a certain threshold.
 9. Theapparatus of claim 8, wherein the apparatus is further to perform:identifying the beam direction for the communication device of thesecond type by determining a beam identification (ID) from thecommunication device of the second type, which reports the beam IDmapped to the beam direction, which has the best receiving power asmeasured by the communication device of the second type.
 10. Theapparatus of claim 9, wherein the communication device of the first typegroups a plurality of communication devices of the second type eachreporting the same beam ID.
 11. The apparatus of claim 9, wherein theapparatus is further to perform: broadcasting a reference signal to theplurality of beam directions, each beam direction corresponding to oneof a plurality of beams of the communication device of the first type.12. The apparatus of claim 8, wherein a respective back-off countervalue for the beam direction within the back-off counter values isobtained by: receiving a value that is less than a generated back-offcounter value, wherein the generated back-off counter value has beenupdated to the value from an earlier listening session.
 13. Theapparatus of claim 12, wherein the apparatus is further to perform: inthe earlier listening session, listening to the beam direction whiledecreasing the generated back-off counter value; upon interference beingdetected in the beam direction, suspending the listening for the beamdirection and stopping the decrease; storing the decreased value; andlistening to another beam direction for transmission to anothercommunication device of the second type.
 14. The apparatus of claim 13,wherein the beam direction has a higher priority than the another beamdirection.
 15. A non-transitory computer readable storage medium,comprising instructions which, when executed on at least one processor,cause the at least one processor to perform operations at acommunications device of a first type, the operations comprising:obtaining back-off counter values, wherein each back-off counter valueis mapped to a respective one of a plurality of beam directions andindicates a medium idle duration in a respective beam direction, when anumber of pending beam directions of the communication device of thefirst type is greater than a number of receiving radio frequency chainsof the communication device of the first type, the plurality of the beamdirections is equal to the number of receiving radio frequency chains,and otherwise the plurality of the beam directions is equal to thenumber of pending beam directions; simultaneously listening to theplurality of beam directions while updating the back-off counter values,each beam direction covering at least one respective communicationdevice of a second type, to which data is to be transmitted; andscheduling transmission of data to a communications device of the secondtype in a beam direction within the plurality of beam directions, whenthe respective back-off counter value mapped to the beam directionreaches a certain threshold.
 16. The non-transitory computer readablestorage medium of claim 15, wherein the operations further comprise:identifying the beam direction for the communication device of thesecond type by determining a beam identification (ID) from thecommunication device of the second type, which reports the beam IDmapped to the beam direction, which has the best receiving power asmeasured by the communication device of the second type.
 17. Thenon-transitory computer readable storage medium of claim 15, wherein arespective back-off counter value for the beam direction within theback-off counter values is obtained by: receiving a value that is lessthan a generated back-off counter value, wherein the generated back-offcounter value has been updated to the value from an earlier listeningsession.